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%I #25 Apr 12 2017 23:09:01
%S 1,-1,-19,-517,-18023,-587529,19183749,12219870323,3379214470193,
%T 883981857320943,238930492488456221,66829754023676225259,
%U 18410558239851140719561,4167711609283156286652647,-82954815883633697917244747,-1284116651310135986426544039581
%N E.g.f. is cos(tan(x)/cos(x)), coefficients of even powers of x.
%C All coefficients of odd powers of x are zero.
%H G. C. Greubel, <a href="/A009081/b009081.txt">Table of n, a(n) for n = 0..235</a>
%t With[{nn=30},Take[CoefficientList[Series[Cos[Tan[x]/Cos[x]],{x,0,nn}], x]Range[0,nn]!,{1,-1,2}]] (* _Harvey P. Dale_, Jan 28 2012 *)
%o (PARI)
%o x='x+O('x^66); /* that many terms */
%o v=Vec(serlaplace(cos(tan(x)/cos(x))));
%o vector(#v\2,j,v[2*j-1]) /* show terms */
%o /* _Joerg Arndt_, Jan 28 2012 */
%K sign
%O 0,3
%A _R. H. Hardin_
%E Extended with signs by _Olivier Gérard_, Mar 15 1997